How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission, above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via the grey wire. The ECU utilizes this information to regulate fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors according to the situation.

If this sensor fails to function, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

It's a bit tricky to test as there are several pins on the connector, and each one has different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should read around 1000 ohms. If you're having issues with this sensor, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge decrease in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, 3 were drenched in gasoline and the 4th was dry. I placed a tissue over each hole in the injector and when i turn the engine on without sparks, the 3 with gazoline jump right out. The 4th one stays closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. I assume that the problem is somewhere else.

I also tried to reset the PID with no success. The car can start if the G28 is disconnected and is running fine when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. I also noticed that the oil gauge in the click here cockpit shows 2 bars while the actual pressure is 0.

I'm not certain what to do, but i feel i have pretty much completely ruled out all other possibilities. But i am afraid I might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 website receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both are used in the 80 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is simple to test them - simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must know the speed and position of the crankshaft to make decisions regarding timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shutdown.

A failing G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, and/or a misfire while in gear. It is probable that your sensor is failing and needs to be replaced if you experience any of these signs. The good news is that they are quite affordable and easy to find, especially if you're looking at the Bosch sensor, which is what ours are. Alternately, GM's version this part is an option.

5. Tachometer

A malfunctioning engine speed sensor could be a cause for a slew of issues with your car. It is a crucial part of the Audi's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear. It sends a signal directly to more info the ECU at pin T55/49, via an uncolored wire. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also sends it to the G5 Tachometer in instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. You should detect an average resistance of 1000 here ohms in these get more info areas. This is a standard part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.